1. Technical Field
The present invention generally relates to an interposer member having apertures for electrically connecting an electronic component to a circuitized substrate. More particular, the present invention relates to an interposer member having a homogeneous elastomer core with strategically positioned apertures for relieving stress and increasing contact compliancy of the member.
2. Background Art
In the production of microelectronics, electronic components (e.g., chip carriers) are often coupled to circuitized substrates (e.g., printed circuit boards). Currently, many methods exist for coupling components to substrates. Such methods include conductive pins, wirebonds, solder balls, etc. A component that is gaining increasing popularity in the field is a Land Grid Array (LGA) module. However, since LGA modules are not configured for direct connection to a substrate, many of the above-cited methods cannot be utilized. Several connectors currently exist for coupling an LGA module to a substrate. One example is the Metallized Polymer Interconnect (MPI) connector by Tyco International. The MPI connector includes a siloxane core with conductive fillers that is positioned between the LGA module and the substrate. However, in order to achieve a desired level of durability (e.g., performance at 70-80xc2x0C. over 5-10 years of operation), extremely slow stress relaxation rates are needed. To obtain slow stress relaxation rates in an elastomeric material such as the MPI connector, a homogeneous elastomer with a low density of unreacted polymer crosslinks and low contaminate contents are needed. These low contents can include low levels of residual cross-linking agents, which can act as contaminants promoting material stress relaxation mechanisms.
Another example of a connecter is shown in U.S. Pat. No. 5,818,700 to Purinton, herein incorporated by reference. Specifically, Purinton discloses a connector having a resin film with unfilled pores for increasing the compressibility of the connector. However, since the connector of Purinton has increased compressibility properties, a requisite level of stiffness is not maintained. Moreover, because the pores will xe2x80x9cbleed outxe2x80x9d (e.g., similar to foamed rubber) and are not strategically positioned, there is no stress relief for any plated through holes or conductive pads that may be positioned on the connector. Without such stress relief, the connector will often fail around the plated through holes and/or the conductive pads.
Other examples of connectors are shown in U.S. Pat. Nos. 4,902,234, 5,059,129 and 5,759,047 all to Brodsky et al., and assigned to the same assignee as the present invention. These references are herein incorporated by reference. None of these references, however, teach an interposer member having a homogeneous elastomer core for maintaining optimum stress relaxation properties. Moreover, none of the references teach an interposer member having strategically positioned apertures through the entire connector for relieving stress (e.g., on the plated through holes and conductive pads of the member) and increasing the contact compliancy of the member.
In view of the forgoing, there exists a need for an interposer member having a homogeneous elastomer core for maintaining optimum stress relaxation properties of the member. Moreover, a need exists for the strategic placement of apertures through the member for relieving stress on plated through holes and conductive pads of the member, and for increasing contact compliancy of the member.
The present invention overcomes the problems of existing connectors by providing an interposer member having a homogeneous elastomer core, and strategically positioned apertures. Specifically, the homogeneous elastomer core provides optimum stress relaxation and stiffness properties while the apertures provide stress relief for any plated through holes and/or conductive pads on the member. Moreover, the apertures provide increased contact compliancy of the member. The apertures are preferably positioned approximately equidistant between two adjacent plated through holes and/or conductive pads so that the stress fields surrounding each plated through hole and conductive pad do not intersect.
According to a first aspect of the present invention, an interposer member having apertures for relieving stress and increasing contact compliancy is provided. The member comprises: (a) a homogeneous elastomer core; (b) a plurality of conductive pads contacting the core; and (c) a plurality of apertures through the member, wherein the apertures are positioned at predetermined locations between adjacent conductive pads.
According to a second aspect of the present invention, an interposer member having apertures for relieving stress and increasing contact compliancy is provided. The member comprises: (a) a homogeneous elastomer core having a plurality of plated through holes; (b) an external flexible layer adhered to an outer surface of the core; (c) a plurality of conductive pads contacting the external flexible layer, wherein a conductive layer is positioned between each pad and the external flexible layer; and (d) a plurality of apertures through the member, wherein the apertures are positioned at predetermined locations between adjacent conductive pads and plated through holes.
According to a third aspect of the present invention, an interposer member having apertures for relieving stress and increasing contact compliancy is provided. The member comprises: (a) a homogeneous elastomer core; (b) a plurality of conductive pads contacting the core; and (c) a plurality of apertures through the member, wherein one of the apertures is positioned approximately equidistant between adjacent conductive pads.
According to a fourth aspect of the present invention, an interposer member having apertures for relieving stress and increasing contact compliancy is provided. The member comprises: (a) a homogeneous elastomer core; (b) an external flexible layer adhered to an outer surface of the core; (c) a plurality of conductive pads contacting the external flexible layer; and (d) a plurality of apertures through the member, wherein one of the apertures is positioned approximately equidistant between adjacent conductive pads.
According to a fifth aspect of the present invention, an interposer member having apertures for relieving stress and increasing contact compliancy is provided. The member comprises: (a) a homogeneous elastomer core having a plurality of plated through holes; (b) an external flexible layer adhered to an outer surface of the core; (c) a plurality of conductive pads contacting the external flexible layer, wherein a conductive layer is positioned between each pad and the external flexible layer; and (d) a plurality of apertures through the member, wherein the apertures are positioned approximately equidistant between adjacent plated through holes and conductive pads.
According to a sixth aspect of the present invention, a method for forming an interposer member having apertures for relieving stress and increasing contact compliancy is provided. The method comprises the steps of: (a) providing a homogeneous elastomer core; (b) positioning conductive pads on the core; and (c) forming a plurality of apertures through the member at predetermined locations between adjacent conductive pads.
According to a seventh aspect of the present invention, a method for forming an interposer member having apertures for relieving stress and increasing contact compliancy is provided. The method comprises the steps of: (a) providing a homogeneous elastomer core having a plurality of apertures; and (b) positioning conductive pads on the core, wherein one of the apertures is positioned approximately equidistant between adjacent conductive pads.
According to an eighth aspect of the present invention, a method for forming an interposer member having apertures for relieving stress and increasing contact compliancy is provided. The method comprises the steps of: (a) providing a homogeneous elastomer core having apertures; (b) adhering an external flexible layer to an outer surface of the core; and (c) positioning a plurality of conductive pads on the flexible layer, wherein one of the apertures is positioned approximately equidistant between adjacent conductive pads.
According to a ninth aspect of the present invention, a method for forming an interposer member having apertures for relieving stress and increasing contact compliancy is provided. The method comprises the steps of: (a) providing a homogeneous elastomer core having a plurality of plated through holes and a plurality of apertures; (b) adhering an external flexible layer to an outer surface of the core; and (c) positioning a plurality of conductive pads on the external flexible layer, wherein a conductive layer is positioned between each pad and the external flexible layer, and wherein the apertures are positioned approximately equidistant between adjacent plated through holes and conductive pads.
Therefore, the present invention provides an interposer member and method for producing the same. The member includes a homogeneous elastomer core having strategically positioned apertures for relieving stress and increasing contact compliancy.